Well you must be very attractive! When they ask you, tell them that you just haven't found the right one yet or something.

Let them continue to be surprised it isn't anything major to worry about.

Why? Do I look like i'm missing something?

Tell them you are a lesbian.

If you know what today's teenage society is like, you'll understand why they are surprised. More and more teenagers are starting to date at younger ages, and consequently many will have boyfriends/girlfriends at an early teen stage. They will sound surprised when you tell them that because they have experienced dating and will most likely be paired with someone else. Don't let their comments get you down. If they ask you why, you ask them in return; why do you care? Does what is happening in my life mean anything to you? Do you feel that you should run my life for me? Chances are they will be taken aback by your comments, because you have had the maturity and courage to stand up for yourself

Usually when a guy says something like that, they are actually trying to convey that they find you very attractive and are surprised that you don't have a boyfriend because they think you must get a lot of offers from potential candidates. It is probably intended as a compliment rather than them thinking you are weird because you don't have a boyfriend, but it does sound a bit odd I admit. When they ask why you don't have one, you can either say a) I'm not really interested in a relationship right now, I have so much going on in my life etc and start to steer the conversation towards something you are really into or busy with, or b) I'm waiting for the right person to come along. Option b) is slightly flirtier and open-ended, leaving open the possibility that he could just be the "right person", so only use this if you are after encouraging a little bit of interest... otherwise I would use option a), which pretty much nips things in the bud and gets the conversation off the subject of you being single. (by the way, I tried to answer your question about 'how to dress sporty' a few minutes ago but realised part way through that I wasn't expressing myself very well and besides, you are probably better off without my fashion advice anyway! but hopefully this answer will be of some use!)

Tell them you are thinking of joining a convent.

They are surprised cause they think that you are way to gorgeous to be single. Tell them what you really feel about why you are single. Then if you like them start talking.(: